Salesforce Deal Should Be Tough Sell

There are some good reasons for companies like Oracle and Microsoft to want to buy Salesforce.com—even if doing so could break the bank.

There are also good reasons not to do it, aside from any financial hit. So while Wall Street’s deal makers may be salivating over the prospect of a megasized software merger that could come in above $50 billion, investors should be wary. History suggests that such efforts in the technology industry...